Fix the detection of multiextruder replacement patterns

Since #3068, replacement patterns can take the form of {setting_nr, extruder_nr}. This form was not being recognised when determining if CuraEngine should prepend its own preheat sequence.

plugins/CuraEngineBackend/StartSliceJob.py

@@ -5,6 +5,7 @@ import numpy
 from string import Formatter
 from enum import IntEnum
 import time
+import re
 
 from UM.Job import Job
 from UM.Application import Application
@@ -337,10 +338,12 @@ class StartSliceJob(Job):
 
         # Pre-compute material material_bed_temp_prepend and material_print_temp_prepend
         start_gcode = settings["machine_start_gcode"]
-        bed_temperature_settings = {"material_bed_temperature", "material_bed_temperature_layer_0"}
-        settings["material_bed_temp_prepend"] = all(("{" + setting + "}" not in start_gcode for setting in bed_temperature_settings))
-        print_temperature_settings = {"material_print_temperature", "material_print_temperature_layer_0", "default_material_print_temperature", "material_initial_print_temperature", "material_final_print_temperature", "material_standby_temperature"}
-        settings["material_print_temp_prepend"] = all(("{" + setting + "}" not in start_gcode for setting in print_temperature_settings))
+        bed_temperature_settings = ["material_bed_temperature", "material_bed_temperature_layer_0"]
+        pattern = r"\{(%s)(,\s?\w+)?\}" % "|".join(bed_temperature_settings) # match {setting} as well as {setting, extruder_nr}
+        settings["material_bed_temp_prepend"] = re.search(pattern, start_gcode) == None
+        print_temperature_settings = ["material_print_temperature", "material_print_temperature_layer_0", "default_material_print_temperature", "material_initial_print_temperature", "material_final_print_temperature", "material_standby_temperature"]
+        pattern = r"\{(%s)(,\s?\w+)?\}" % "|".join(print_temperature_settings) # match {setting} as well as {setting, extruder_nr}
+        settings["material_print_temp_prepend"] = re.search(pattern, start_gcode) == None
 
         # Replace the setting tokens in start and end g-code.
         # Use values from the first used extruder by default so we get the expected temperatures